He concludes that "even with $10 gasoline and sunshine, lollipops and roses battery cost figures, the Return on Incremental Battery Investment (ROIBI) falls off a cliff as soon you move beyond the Prius"

Peterson then shares this great quote from Bill Reinert, Toyota's manager of advanced technology: “I used to be a big 100-miles-per-gallon guy. But I realized that we’re above the level of diminishing returns at 50 miles per gallon. So why not make a whole bunch of 50-miles-per-gallon cars and put people who are driving 20-miles-per-gallon cars into them?” (Here's a link to the original article from automobilemag.com.)